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Abstract:

A method of controlling a boiler plant during a switchover period from an
air-combustion mode to an oxygen-combustion mode. The method includes
steps of feeding fuel into a furnace of the boiler plant at a rate
determined by a fuel feeding scheme, feeding air into the furnace at a
rate determined by a descending air feeding scheme, feeding substantially
pure oxygen into the furnace at a rate determined by an ascending oxygen
feeding scheme, and recirculating flue gas into the furnace at a rate
determined by an ascending flue gas recirculating scheme. The fuel
feeding scheme, the air feeding scheme and the oxygen feeding scheme are
such that the fuel is combusted and the flue gas containing residual
oxygen is produced. Also, the fuel feeding scheme, the air feeding scheme
and the oxygen feeding scheme are such that the content of residual
oxygen in the flue gas is, during at least a portion of the switchover
period, greater than during any of the air-combustion mode and the
oxygen-combustion mode. The method makes it possible to reduce CO2
emissions and O2 consumption quickly during the short switchover
period.

Claims:

1. A method of controlling a boiler plant during a switchover period from
an air-combustion mode to an oxygen-combustion mode, the method
comprising the steps of: (a) feeding fuel into a furnace of the boiler
plant at a rate determined by a fuel feeding scheme; (b) feeding air into
the furnace at a rate determined by a descending air feeding scheme; (c)
feeding substantially pure oxygen into the furnace at a rate determined
by an ascending oxygen feeding scheme; and (d) recirculating flue gas
into the furnace at a rate determined by an ascending flue gas
recirculating scheme, wherein (i) the fuel feeding scheme, the air
feeding scheme and the oxygen feeding scheme are such that the fuel is
combusted and flue gas containing residual oxygen is produced, and (ii)
the fuel feeding scheme, the air feeding scheme and the oxygen feeding
scheme are such that the content of the residual oxygen in the flue gas
is, during at least a portion of the switchover period, greater than
during any of the air-combustion mode and the oxygen-combustion mode.

2. The method according to claim 1, wherein the amount of the residual
oxygen is, during at least a portion of the switchover period, at least
100% greater than during any one of the air-combustion mode and the
oxygen-combustion mode.

3. The method according to claim 2, wherein the amount of residual oxygen
is, during at least a portion of the switchover period, at least 200%
greater than during any one of the air-combustion mode and the
oxygen-combustion mode.

4. The method according to claim 2, wherein the amount of residual oxygen
is, during at least a central fourth of the switchover period, at least
100% greater than during any of the air-combustion mode and the
oxygen-combustion mode.

5. The method according to claim 3, wherein the amount of residual oxygen
is, during at least a central fourth of the switchover period, at least
200% greater than during any of the air-combustion mode and the oxygen
combustion mode.

6. The method according to claim 4, wherein the amount of residual oxygen
is, during at least a third of the switchover period, scheduled mostly at
the second portion of the switchover period, at least 100% greater than
during any of the air-combustion mode and the oxygen-combustion mode.

7. The method according to claim 5, wherein the amount of residual oxygen
is, during at least a third of the switchover period, scheduled mostly at
the second portion of the switchover period, at least 200% greater than
during any of the air-combustion mode and the oxygen-combustion mode.

8. The method according to claim 1, wherein the boiler plant comprises an
oxygen storage, and, during the switchover period, at least a portion of
the substantially pure oxygen is fed to the furnace from the oxygen
storage.

9. The method according to claim 8, wherein oxygen is stored into the
oxygen storage during the air-combustion mode.

10. The method according to claim 1, wherein the descending air feeding
scheme deviates from a linear descent to zero by at most 40% of the air
feeding rate at the beginning of the switchover period.

11. The method according to claim 10, wherein the descending air feeding
scheme deviates from a linear descent to zero by at most 20% of the air
feeding rate at the beginning of the switchover period.

12. The method according to claim 1, wherein the ascending flue gas
recycling scheme deviates from a linear ascent from zero to flue gas
recycling rate at the beginning of the oxygen-combustion mode by at most
40% of the flue gas recycling rate at the beginning of the
oxygen-combustion mode.

13. The method according to claim 12, wherein the ascending flue gas
recycling scheme deviates from a linear ascent from zero to flue gas
recycling rate at the beginning of the oxygen-combustion mode by at most
20% of the flue gas recycling rate at the beginning of the
oxygen-combustion mode.

14. The method according to claim 1, wherein the fuel feeding scheme is
substantially constant and is equal to the fuel feeding rate at the
beginning of the oxygen-combustion mode.

15. The method according to claim 1, wherein the fuel feeding scheme, the
air feeding scheme, the oxygen feeding scheme and the flue gas
recirculating scheme are such that deviations in the mass flow rate of
the flue gas discharged from the furnace during the switchover period are
within 10% of the average.

Description:

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a method of controlling a boiler
plant during a switchover period from an air-combustion mode to an
oxygen-combustion mode. The invention particularly relates to a method
comprising the steps of feeding solid carbonaceous fuel into a furnace of
the boiler plant at a rate determined by a fuel feeding scheme, feeding
air into the furnace at a rate determined by a descending air feeding
scheme, feeding substantially pure oxygen into the furnace at a rate
determined by an ascending oxygen feeding scheme, and recirculating flue
gas into the furnace at a rate determined by an ascending flue gas
recirculating scheme, wherein the fuel feeding scheme, the air feeding
scheme and the oxygen feeding scheme are such that the fuel is combusted
and flue gas containing residual oxygen is produced.

[0003] 2. Description of the Related Art

[0004] Coal-fired power plants currently account for more than 40% of
man-made world-wide carbon dioxide emissions. Oxygen-combustion, also
called oxyfuel combustion, is one of the generally known methods of
removing carbon dioxide from the exhaust gas of a power plant combusting
coal, or other solid carbonaceous fuels. Oxygen-combustion is based on
combusting solid carbonaceous fuel with substantially pure oxygen, to
produce carbon dioxide and water vapor as the main components of the flue
gas. This allows the carbon dioxide to be much more easily captured from
the flue gas than in air-combustion, where nitrogen is the dominant flue
gas component.

[0005] In oxygen-combustion, the fuel is advantageously combusted by using
an oxidant consisting of substantially pure oxygen, obtained from an air
separation unit (ASU), mixed with recycled flue gas. The products of
combustion are then only CO2, water vapor, and a relatively small
amount of impurities. The water vapor is condensed in the flue gas
channel, yielding a nearly-pure CO2 stream ready for sequestration.
The CO2 effluent is then cooled and compressed to high pressure, and
the resultant liquid or supercritical CO2 is piped from the plant to
be sequestered in geologic formations. The use of an oxidant consisting
of oxygen and recycled flue gas renders it possible to adjust the
combustion conditions to nearly similar to those of conventional
air-combustion boilers.

[0006] Due to the uncertainties in, for example, the CO2 capture and
storage technology, there is a need for boilers that can be changed from
air-combustion to oxygen-combustion, and vice-versa, with minimal changes
in the plant equipment. Correspondingly, it is advantageous to be able to
operate an oxygen-combustion boiler in an air-combustion mode, for
example, when the ASU, CO2 purification and compression unit (CPU),
or CO2 storage system is unavailable. Moreover, the flexibility to
operate a boiler in either an air-combustion or an oxygen-combustion mode
allows adjustment of plant operation to a changing and unknown market for
carbon-free electricity, and will promote faster adoption of carbon
capture and sequestration technology.

[0007] A boiler design that is capable of running on either air-combustion
or oxygen-combustion is adaptable to a new boiler or a retrofit of an
existing boiler. By properly selecting the flue gas recirculation flow
rate, the same boiler geometry, materials, and burners, etc., can be used
in both air-combustion and oxygen-combustion modes at all loads. The
oxygen-combustion process can readily be retrofitted to an existing
boiler by adding the flue gas recycling equipment, the air separation
unit, and the CO2 compression and purification equipment.

[0008] It would be useful to be able to switch a boiler from
air-combustion or oxygen-combustion online, i.e., without interrupting or
seriously distracting the combustion process. Especially, when using a
process where an oxygen-combustion boiler is started with air-combustion,
it is necessary to be able to safely switch online, at full load or
partial load, from air-combustion to oxygen-combustion. During the
switchover period, the flue gas will be purged to the stack instead of
the CPU, until the flue gas reaches a certain CO2 concentration.
Thus, in order to reduce O2 consumption and CO2 emission, a
fast switchover is desired. A fast switchover, however, tends to
adversely affect the boiler performance, such as superheat and reheat
steam temperatures. Thus, there is a need for proper dynamic control to
assure continuous and safe operation of the plant during a fast
switchover from air-combustion or oxygen-combustion.

SUMMARY OF THE INVENTION

[0009] An object of the present invention is to provide a method of
controlling a boiler plant during a switchover period from an
air-combustion mode to an oxygen-combustion mode.

[0010] Another object of the present invention is to allow a fast
switchover from an air-combustion mode to an oxygen-combustion mode, in
order to reduce CO2 emission and O2 consumption during the
switchover period.

[0011] In order to obtain this and other objects, the present invention
provides a method of controlling a boiler plant during a switchover
period from air-combustion mode to an oxygen-combustion mode. The method
comprises the steps of feeding fuel into a furnace of the boiler at a
rate determined by a fuel feeding scheme, feeding air into the furnace at
a rate determined by a descending air feeding scheme, feeding
substantially pure oxygen into the furnace at a rate determined by an
ascending oxygen feeding scheme, and recirculating flue gas into the
furnace at a rate determined by an ascending flue gas recirculating
scheme, wherein the fuel feeding scheme, the air feeding scheme and the
oxygen feeding scheme are such that the fuel is combusted, and flue gas
consisting of an amount of residual oxygen is produced, and wherein the
fuel feeding scheme, the air feeding scheme and the oxygen feeding scheme
are such that the content of residual oxygen in the flue gas is, during
at least a portion of the switchover period, greater than during any of
the air-combustion mode and the oxygen-combustion mode.

[0012] When combusting solid carbonaceous fuel in a boiler, for example,
in a PC-boiler or a CFB-boiler, the oxygen feeding rate is generally
slightly higher than what is theoretically needed for complete combustion
of the fuel. The amount of unburned carbon in the ash discharged from the
furnace of a boiler, as well as overall emissions of carbon monoxide and
NOx are generally minimized when the oxidant feeding rate is such
that the flue gas discharged from the furnace contains about 3-4% oxygen,
so-called residual oxygen.

[0013] The oxygen/fuel ratio, i.e., the ratio of the feeding rates of
oxygen and fuel, is advantageously adjusted during the switchover period,
so that the amount of residual oxygen in the flue gas is, during at least
a portion of the switchover period, greater, preferably, at least 100%
greater, and more preferably, at least 200% greater, than during any of
the air-combustion mode and the oxygen-combustion mode. The residual
oxygen level is advantageously obtained by increasing the oxygen feeding
rate so as to provide a fast response through increasing the combustion
rate of the boiler by combusting accumulated fuel, such as char in a CFB
bed or coal in a coal mill.

[0014] The content of residual oxygen during the air-combustion mode and
oxygen-combustion mode refers here to a typical, or aimed, residual
oxygen content of the flue gas during a steady state air-combustion
process before the switchover period and during a steady state
oxygen-combustion process after the switchover period. Typically, the
residual oxygen content of the flue gas is, according to the present
invention, during at least a portion of the switchover period, clearly
greater than 3-4%, preferably, at least 6-8%, and even more preferably,
at least 9-12%. By this way, a short switchover period, for example,
about five minutes, can be reached, which significantly reduces the
CO2 emission and O2 consumption during switchover.

[0015] According to a simulation calculation, a smooth, safe and fast
switchover from air-combustion to oxygen-combustion was obtained when the
residual oxygen content of the flue gas was about 16% during a portion of
the switchover period. It was surprisingly observed in the simulation
calculation that such a high residual oxygen level is desired in order to
achieve smooth changing of the furnace outlet temperature, to minimize
unburned fuel in the ash, and to maintain a desired power plant output
during the switchover.

[0016] The residual oxygen content of the flue gas may advantageously vary
during the switchover period so that it corresponds at the beginning and
at the end of the switchover period to the aimed residual oxygen content
during the air-combustion mode and oxygen-combustion mode, respectively,
but is, during a central portion of the switchover period, greater than
during any of the air-combustion mode and the oxygen-combustion mode.
According to a preferred embodiment of the present invention, the amount
of residual oxygen is, during a central fourth of the switchover period,
greater, preferably, at least 100% greater, and more preferably, at least
200% greater, than during any of the air-combustion mode and the oxygen
combustion mode. A central fourth of the switchover period here refers to
a portion of the switchover period, which lasts a fourth of the duration
of the switchover period and extends to the point of time being at the
center of the switchover period. Naturally, the length of the portion of
the switchover period having an increased residual oxygen content may be
longer than a fourth of the switchover period. The limit, one fourth,
states only an advantageous minimum length of the portion of the
switchover period having an increased residual oxygen content.

[0017] According to another preferred embodiment of the present invention,
the amount of residual oxygen is, during a third of the switchover
period, located mostly at the second portion of the switchover period,
greater, preferably at 100% greater, more preferably, at least 200%
greater, than during any of the air-combustion mode and the
oxygen-combustion mode. A third of the switchover period, located mostly
at the second portion of the switchover period, here refers to a portion
of the switchover period, which lasts a third of the duration of the
switchover period and extends for more than one half of its duration
after the point of time at the center of the switchover period.
Naturally, the length of the portion of the switchover period having an
increased residual oxygen content may be longer than a third of the
switchover period.

[0018] The main feature of the switchover period is that the air feeding
rate decreases from an initial value to zero, and the oxygen feeding rate
increases from zero to a final value. Moreover, in order, for example, to
maintain the furnace temperature at a suitable level, the flue gas
recirculation rate increases from a small value, typically, from zero, to
a final value, which typically corresponds to 70-80% of the flue gas
flow.

[0019] Assuming that there is no particular reason to decrease the output
power of the boiler plant during the switchover from air-combustion to
oxygen-combustion, the fuel feeding rate may be maintained at a constant
level from the end of the air-combustion mode to the beginning of the
oxygen-combustion mode, i.e., throughout the switchover period. However,
the fuel feeding rate may, advantageously, be increased when switching
from air-combustion to oxygen-combustion, so as to minimize the decrease
of the output power of the plant, as described in U.S. patent application
publication number 2009/0260585 A1. Moreover, according to a preferred
embodiment of the present invention, the fuel feed rate is increased
during the switchover period, so as to maintain superheater and reheater
outlet temperatures during the switchover period within acceptable
limits.

[0020] If the fuel feeding rate is changed, it may advantageously be
changed at the beginning of the switchover period, to be then maintained
constant during the switchover period. Alternatively, the fuel feeding
rate may be changed during the switchover period according to another
advantageous scheme. Coal accumulation in a coal mill of a PC-boiler, or
bed char inventory of a CFB-boiler, can be utilized in parallel to a fuel
feed rate adjustment to obtain a fast increase in the fuel combustion
rate, if desired. By controlling superheater and reheater temperatures
during switchover from air-combustion to oxygen-combustion, metal
material damage can be avoided and power plant output can be maintained.
By maintaining a minimum acceptable content of residual oxygen in the
flue gas, unburned fuel can be minimized and power plant output can be
maintained.

[0021] According to a preferred embodiment of the present invention, the
air feeding rate descends from an initial value to zero according to a
predetermined, approximately linear scheme. The descending air feeding
scheme deviates during the switchover period from a linear descent, from
the initial value at the beginning of the switchover period to zero,
preferably, by at most 40%, even more preferably, by at most 20%, of the
air feeding rate at the beginning of the switchover period.

[0022] According to another preferred embodiment of the present invention,
the flue gas recycling rate ascends from zero to a final value according
to a predetermined, approximately linear scheme. The ascending flue gas
recycling scheme deviates during the switchover period from a linear
ascent, from zero to the final value, the value at the beginning of the
oxygen-combustion mode, preferably, by at most 40%, even more preferably,
by at most 20%, of the final flue gas recycling rate at the beginning of
the oxygen-combustion mode.

[0023] The fuel feeding scheme, air feeding scheme, oxygen feeding scheme
and flue gas recirculating scheme are advantageously such that the mass
flow rate of the flue gas is approximately constant during the switchover
period. Preferably, in order to obtain a smooth transition from
air-combustion to oxygen-combustion, the deviations in the mass flow rate
of the flue gas discharged from the furnace during the switchover period
are within 10% of the average of the mass flow rate of the flue gas.

[0024] The content of the residual oxygen in the flue gas may
advantageously be increased during the switchover period by suitably
increasing the feeding rate of substantially pure oxygen into the
furnace. It may, however, not be possible to obtain a sufficiently
increased stream of oxygen from an ASU. Therefore, according to a
preferred embodiment of the present invention, the boiler plant comprises
a storage of oxygen, preferably, a storage of liquid oxygen, and during
the switchover period, at least a portion of the substantially pure
oxygen is fed to the furnace from the oxygen storage. The oxygen may be
stored into the oxygen storage at any time before the switchover period.
However, oxygen is advantageously stored into the oxygen storage during
the air-combustion mode.

[0025] According to the present invention, the fuel feeding scheme, the
air feeding scheme and the oxygen feeding scheme are not independent, but
they are related so that the residual oxygen in the flue gas is, during
at least a portion of the switchover period, greater than that during any
of the air-combustion mode and oxygen-combustion mode. Thus, the ratio of
the total oxygen fed to the furnace, i.e., oxygen from the air and oxygen
from the substantially pure oxygen, to the fuel fed to the furnace is
such that the desired level of residual oxygen in the flue gas is
obtained. Once the period of the switchover is complete, the fuel feeding
rate and the oxygen/coal ratio will be maintained at the steady state
value.

[0026] The above brief description, as well as other objects, features and
advantages of the present invention will be more fully appreciated by
reference to the following detailed description of the currently
preferred, but nonetheless illustrative, embodiments and examples of the
present invention, taken in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING

[0027]FIG. 1 is a schematic diagram of an oxyfuel combustion boiler plant
in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0028]FIG. 1 shows a schematic diagram of an oxygen-combustion boiler
plant 10 in accordance with an embodiment of the present invention. The
boiler plant 10 comprises a PC-boiler 12 with a furnace 14, a flue gas
channel 16 leading to a CO2 purification and compression unit (CPU)
18, and a flue gas recycling channel 20. The flue gas recycling channel
comprises means, such as a damper 22 and a variable speed fan 24, for
controlling the flue gas circulation rate.

[0029] The boiler plant 10 comprises an air separation unit (ASU) 26,
which produces a stream of substantially pure oxygen by separating
nitrogen from a stream of air 28. An oxygen channel 30 leads the stream
of substantially pure oxygen from the ASU to a mixer 32, where the oxygen
is mixed with recycled flue gas from the flue gas recycling channel 20.
The mixer produces primary oxidant gas, which is led along a primary
oxidant channel 34 to a coal mill 36. A feed stream of coal 38 is crushed
in the coal mill 36 to pulverized coal, which is conducted together with
the primary oxidant gas along a fuel feeding channel 40 to a burner 42
attached to the furnace 14. In practice, there are multiple burners
attached to the furnace 14, but, for the sake of simplicity, only one is
shown in FIG. 1. The coal is combusted in the furnace 14 by the primary
oxidant gas and a secondary oxidant gas, which is led from the mixer 32
via a secondary oxidant channel 44 and a wind box 46 to the furnace. Part
of the substantially pure oxygen, as required, may be fed to the burner
42 directly, without being mixed with the recirculated gas.

[0030] The boiler plant 10 also comprises an inlet for air 48, so as to
render possible to use, when desired, air as an oxidant, instead of a
mixture of oxygen and recycled flue gas. The inlet for air 48 is
advantageously connected to the flue gas recycling channel 20, but it may
alternatively be connected to the boiler 12 with, for example, a separate
air channel. The inlet for air 48 comprises means, such as a damper 50,
for controlling the rate of feeding air.

[0031] The flue gas channel 16 leads flue gas from the furnace 14 via heat
exchange surfaces, such as conventional superheaters and reheaters 52,
economizers 54, a gas-gas heat exchanger 56, used for heating recycled
flue gas or air, and gas cleaning units, such as a dust separator 58, to
the CPU 18. The flue gas channel 16 may also comprise other flue gas
cleaning units, such as an NOx catalyst or a sulfur capturing unit,
but they are not shown in FIG. 1, because they are not relevant for the
present invention.

[0032] A stack 60 for leading cleaned flue gas to the environment is also
connected to a side branch 62 of the flue gas channel 16. Flue gas can be
conducted to the stack 60 in case the CPU 18 is not in use, for example,
when starting-up the boiler plant 10, or when the boiler plant 10 is used
in an air-combustion mode. The side branch 62 and the end portion of the
flue gas channel 16 are equipped with means, such as dampers 64, 64', for
directing the flue gas either to the CPU 18 or to the stack 60.

[0033] An oxygen storage 66, with an inlet damper 68 and an outlet damper
70, is advantageously connected parallel with a portion of the oxygen
channel 30. By opening the inlet damper 68 while closing or throttling a
damper 72 arranged in the oxygen channel 30, it is then possible to store
oxygen produced in the ASU 26 into the oxygen storage 66, when the boiler
plant is in the air-combustion mode, or the oxygen demand is less than
the production capability of the ASU. The stored oxygen can then be used
for combustion, by opening the damper 70, when the oxygen demand is
higher than the production capability of the ASU.

[0034] The operation mode of the boiler plant 10 is controlled by a
control unit 74. While the boiler plant is in an oxygen-combustion mode,
the ASU 26 is operating, the damper 72 in the oxygen channel is open, the
damper 50 for controlling the feeding of air is closed, the damper 22 in
the flue gas recycling channel 20 is open, the fan 24 in the recycling
channel 20 is operating, the CPU 18 is operating, the damper 64' in the
end portion of the gas channel is open, and the damper 64 in the side
branch 62 of the flue gas channel 16 is closed. Correspondingly, when the
boiler plant 10 is in the air-combustion mode, the ASU 26 does not have
to be operating, the damper 72 in the oxygen channel 30 is closed, the
damper 50 for controlling the feeding of air is open, the damper 22 in
the flue gas recycling channel 20 is closed or nearly closed, the fan 24
in the recycling channel is operating, the CPU 18 is not operating, the
damper 64' in the end portion of the flue gas channel 16 is closed, and
the damper 64 in the side branch 62 of the flue gas channel 16 is open.

[0035] During a switchover from the air-combustion mode to the
oxygen-combustion mode, the feeding of air to the furnace 14 is gradually
decreased to zero by gradually closing the damper 50 for controlling the
feeding of air. Simultaneously, the feeding of oxygen to the furnace 14
is gradually increased by gradually opening the damper 72 in the oxygen
channel 30, after starting the operation of the ASU. Simultaneously, the
recycling of the flue gas is also started, or increased, by gradually
opening the damper 22 in the flue gas recycling channel 20. The feeding
of coal along the fuel feeding channel 40 is advantageously increased to
a higher level during the switchover, but it may, in some applications,
also be maintained at a constant level.

[0036] According to the present invention, the feeding of coal, oxygen and
air are advantageously controlled during the switchover period from
air-combustion to oxygen-combustion by the control unit 74, so as to
increase the level of residual oxygen in the flue gas channel during at
least a portion of the switchover period, to be clearly higher than
typically during the operation of the boiler in any of the air-combustion
mode and the oxygen-combustion mode. The change of the coal, oxygen and
air feeding rates, as well as the flue gas recycling rate is
advantageously based on predetermined schemes, which are known to result
in the desired residual oxygen level. The descending air feeding scheme
and the ascending flue gas recycling scheme are advantageously
approximately linear functions, but they may, in some cases, also be of
some other suitable form. The actual residual oxygen level in the flue
gas is advantageously measured by a sensor 76 arranged in the flue gas
channel 16, so as to adjust the above-mentioned schemes.

[0037] The present invention is described above in connection with an
oxyfuel-combustion PC-boiler, but the invention can, as well, be used in
a CFB boiler. Then, as is clear to a person skilled in the art, the fuel
is not limited to coal, but it may, alternatively, be other kinds of
solid fuel, such as, for example, biofuel or waste derived fuel. As is
generally known, the means for feeding fuel and oxidant differ in the
case of a CFB boiler from that of a PC-boiler, but the main features of
the present invention, as described above, are essentially unchanged.

[0038] While the invention has been described herein by way of examples in
connection with what are, at present, considered to be the most preferred
embodiments, it is to be understood that the invention is not limited to
the disclosed embodiments, but is intended to cover various combinations
or modifications of its features, and several other applications included
within the scope of the invention as defined in the appended claims.

Patent applications by Andrew Seltzer, Livingston, NJ US

Patent applications by Horst Hack, Hampton, NJ US

Patent applications by Zhen Fan, Parsippany, NJ US

Patent applications by FOSTER WHEELER NORTH AMERICA CORP.

Patent applications in class Controlling or proportioning feed

Patent applications in all subclasses Controlling or proportioning feed